Electromagnetic wave source probing device and probing method with the probing device

ABSTRACT

A quite novel electromagnetic wave source probing device and a method with such a device in which the probing time can be shortened. Magnetic field to time characteristics generated from a subject to be measured are measured in a plurality of positions. Electric field to frequency characteristics generated from the subject to be measured are calculated by use of the plurality of measured magnetic field to time characteristics. Frequency components exceeding a predetermined electric field value are extracted in the calculated electric field to frequency characteristics. Positions where currents having the extracted frequency components exist in the subject to be measured are outputted.

BACKGROUND OF THE INVENTION

[0001] The present invention relates to a method and a device forprobing a source of electromagnetic waves generated from electronicequipment or the like, and particularly relates to a method and a deviceadapted for probing a source of electromagnetic waves in a short time.

[0002] In the unnecessary electromagnetic radiation control technique,electromagnetic interference occurs frequently asinformation/communication equipment and so on come into wide userecently, and technique for detecting a source of electromagnetic wavescausing the interference is required. As for the system for probing asource of electromagnetic waves, there are papers, for example, byJunichi Kikuchi, “A Suggestion for a Method of Estimating the Positionof a Source of Electromagnetic Waves by Aperture Combination”, IEICE(the Institute of Electronics, Information and Communication Engineersof Japan), Transactions B-IJ, October 1985; Junichi Kikuchi, “PositionalEstimation of a Source of Electromagnetic Waves with Maximum EntropyMethod”, IEICE Transactions B-II, September 1986; Masayo Hayashi,“Electromagnetic Field Measurement and Numerical Analysis in EMC”, NECTechnical Report, September 1993; etc.

[0003]FIG. 5 shows such a conventional method for probing a source ofelectromagnetic waves.

[0004] First, in the conventional probing method, frequency to electricfield intensity characteristics E(f) at a distance of 3 m or 10 m whichwas a target of legal controls was measured (Step 501), and frequencycomponents which did not satisfy a regulation value were extracted fromthe results of the measurement (Step 502). Electromagnetic fielddistribution near a subject to be measured was measured with respect tothe extracted frequency components (Step 503), and places (positions) tobe coped with in the subject to be measured were specified from theresults of the measurement (Step 504).

[0005] It was therefore necessary to measure both the distant field andthe near field before the places to be coped with were specified. Inaddition, when there were many frequency components which did notsatisfy the regulation value, it was necessary to measureelectromagnetic field distribution near the subject to be measuredcorresponding to the number of the frequency components which did notsatisfy the regulation value. Accordingly, there was a problem that thewhole probing period of time was prolonged.

SUMMARY OF THE INVENTION

[0006] It is therefore an object of the present invention to provide aquite novel electromagnetic wave source probing device and a methodthereof, in which the probing time can be shortened. That is, it is anobject of the present invention to provide an electromagnetic wavesource probing device and a method thereof, in which it is not necessaryto perform conventional measurement of electromagnetic field strengthdistribution near a subject to be measured with respect to respectivefrequency components.

[0007] In order to attain the foregoing object, according to the presentinvention, prospect is performed by using a near magnetic field measuredvalue H(t) in time domain, differently from a conventional prospect byusing a distant electric field measured value E(f) in frequency domain.

[0008] More specifically, according to an aspect of the presentinvention, provided is an electromagnetic wave source probing methodcomprising the steps of: measuring magnetic field to timecharacteristics generated from a subject to be measured in a pluralityof positions; calculating electric field to frequency characteristicsgenerated from the subject to be measured by use of the plurality ofmeasured magnetic field to time characteristics; extracting frequencycomponents exceeding a predetermined electric field value in thecalculated electric field to frequency characteristics; and outputtingpositions where currents having the extracted frequency components existin the subject to be measured.

[0009] According to another aspect of the present invention, provided isan electromagnetic wave source probing device comprising: a plurality ofmeasuring means for measuring magnetic field to time characteristicsgenerated from a subject to be measured; a first calculating means forcalculating electric field to frequency characteristics generated fromthe subject to be measured based on the magnetic field to timecharacteristics measured by the plurality of measuring means; a secondcalculating means for calculating frequency components exceeding apredetermined electric field value in the calculated electric field tofrequency characteristics; and an output means for outputting positionswhere currents having the calculated frequency components exist in thesubject to be measured.

[0010] In such a manner, it is not necessary to measure both the distantfield and the near field, unlike a conventional case, before places tobe coped with are specified, but it will go well if only the near fieldis measured. It is therefore possible to shorten the prospect time.Particularly, even if there are many frequency components which do notsatisfy the regulation value, it is not necessary to measureelectromagnetic field distribution near the subject to be measuredcorresponding to the number of the frequency components unlike theconventional case, and the places to be coped with can be specifiedsimply by a calculation process simply. It is therefore possible toshorten the probing time on a large scale.

BRIEF DESCRIPTION OF THE DRAWINGS

[0011]FIG. 1 is a diagram illustrating the configuration of anelectromagnetic wave source probing device according to the presentinvention;

[0012]FIG. 2 is a conceptual diagram of a back-calculation system for anelectromagnetic wave source according to the present invention;

[0013]FIG. 3 is a flow chart of an electromagnetic wave source probingsystem according to the present invention;

[0014]FIG. 4 is a flow chart showing a procedure of processing in thissystem; and

[0015]FIG. 5 is a flow chart showing a conventional procedure ofprocessing.

DETAILED DESCRIPTION OF THE EMBODIMENT

[0016] An embodiment of the present invention will be described indetail below with reference to the drawings.

[0017]FIG. 1 shows the system configuration of the embodiment.

[0018] In FIG. 1, the reference numeral 101 represents a subject to bemeasured; 106, a three-dimensional magnetic field probe in which anx-direction magnetic field probe 103, a y-direction magnetic field probe104 and a z-direction magnetic field probe 105 are combined; 107, ahigh-frequency amplifier; 108, a phase detector; 109, an A/D converter;110, an arithmetic computer; and 112, a sampling start clock forsupplying a clock to the phase detector 108. In a direct probing system,there would arise influence of a mirror image caused by a measuringdevice. Accordingly, in this embodiment, in order to reduce thisinfluence, a distance is set between a measuring device body and asubject to be measured, and only the magnetic field probe which is smallenough not to disturb the magnetic field is extended from the measuringdevice body to the subject to be measured. Then, measurement isperformed.

[0019] The three-dimensional magnetic field probe 106 is constituted bythree loop antennas 103, 104 and 105. The loop antennas 103, 104 and 105are disposed so that their loop surfaces are directed in theX-direction, the Y-direction and the Z-direction respectively. With theloop antennas, magnetic field intensity can be measured by inductionvoltage induced in the loop antennas. In addition, the three-dimensionalmagnetic field probe 106 is disposed at a point which is apart from thesubject to be measured 101 by a distance 102. For example, thethree-dimensional magnetic field probe 106 is disposed so as to be veryclose to the subject to be measured 101, that is, at a distance of about1 cm. In addition, though not shown, a plurality of three-dimensionalmagnetic field probes 106 are arranged at intervals of about 1 cm in thelongitudinal and transverse directions so as to cover the subject to bemeasured 101. That is, the three-dimensional magnetic field probes 106are arranged in the form of a so-called lattice.

[0020] Next, the operation in this system will be described.

[0021] First, when measurement is started, the three-dimensionalmagnetic field probe 106 in which the x-direction magnetic field probe103, the y-direction magnetic field probe 104 and the z-directionmagnetic field probe 105 are combined detects a magnetic field generatedfrom the subject to be measured 101. That is, the three-dimensionalmagnetic field probe 106 detects induction voltages which are changed bymagnetic flux passing through the loop antennas 103 to 105 respectively.The detected induction voltages are amplified by the high-frequencyamplifier 107, and applied to the phase detector 108. At that time, theloop antennas 103 to 105 detect the induction voltages in the form oftime waveforms.

[0022] A clock synchronized with the cycle operation period of thesubject to be measured 101 is supplied from the sampling start clock 112to the phase detector 108. The phase detector 108 samples the timewaveforms of the above-mentioned induction voltages on the basis of thisclock. Consequently, it is possible to obtain information of size andphase about the induction voltages. Here, the time to measure theinduction voltages is made to be not shorter than 1/fs [sec] where fs[Hz] designates a lower limit frequency to be probed. In addition,sampling frequency of the time waveform required for probing is made tobe not shorter than 2fe [Hz] where fe [Hz] designates an upper limitfrequency to be probed. These are conditions on the basis of generalsampling theorem.

[0023] Next, signals about the information of the size and phase of thesampled induction voltages are A/D converted by the A/D converter 109.The converted signals are read by the arithmetic computer 110. Thearithmetic computer 110 converts this information about the inductionvoltages into information about magnetic field by use of a predeterminedtransformation to thereby obtain magnetic field to time characteristicsH(t).

[0024]FIG. 4 shows a method in which this time information (magneticfield to time characteristics H(t)) about magnetic field is used forprobing a source of electromagnetic waves in a subject to be measured.This processing is also performed by the arithmetic computer 110.

[0025] First, current to time characteristics I(t) on the subject to bemeasured are calculated on the basis of the above-mentioned magneticfield to time characteristics H(t) (practically on the basis of theintensity of the magnetic field per sampling time) (Step 401). Forexample, the current to time characteristics I(t) on the subject to bemeasured are calculated on the basis of the magnetic field to timecharacteristics H(t) by use of the fact that an electric current Ix(n)existing in the subject to be measured, and calculated values Hx, y, zx, y, z (m, n) and measured values Hmx, y, z (m) of a neighbor magneticfield generated by the current Ix(n) have a relation of Expression 1. Inthe term “Hx, y, z x, y, z (m, n)”, x, y and z adjacent to H on theright designate directional components of a magnetic field; x, y and zadjacent to these x, y and z on the right designate directionalcomponents of an assumed electric current, and (m, n) designate aposition where the magnetic field is measured and a position where thecurrent is assumed. On the other hand, in the term “Hmx, y, z (m)”, Hmdesignates a measured value; x, y and z adjacent thereto on the rightdesignate directional components of the magnetic field; and (m)designates a position where the magnetic field is measured.$\begin{matrix}{\begin{pmatrix}{{Hm}_{x}(m)} \\{{Hm}_{y}(m)} \\{{Hm}_{z}(m)}\end{pmatrix} = {\begin{pmatrix}{{{Hx}_{x}( {m,n} )},{{Hx}_{y}( {m,n} )},{{Hx}_{z}( {m,n} )}} \\{{{Hy}_{x}( {m,n} )},{{Hy}_{y}( {m,n} )},{{Hy}_{z}( {m,n} )}} \\{{H\quad {z_{x}( {m,n} )}},{H\quad {z_{y}( {m,n} )}},{H\quad {z_{z}( {m,n} )}}}\end{pmatrix} \cdot \begin{pmatrix}{I_{x}(n)} \\{I_{y}(n)} \\{I_{z}(n)}\end{pmatrix}}} & \text{Expression~~1}\end{matrix}$

[0026] That is, the simultaneous equations of Expression 1 are solved byusing the data per sampling time, so that the current to timecharacteristics I(t) on the subject to be measured are calculated on thebasis of the magnetic field to time characteristics H(t).

[0027] The calculated current to time characteristics I(t) and theposition on the subject to be measured are stored in association witheach other.

[0028] Next, the current to time characteristics I(t) are regarded as asource of micro-dipole waves in a position on the subject to bemeasured, and an electric field E(t) in a position at a distance whichis a target of legal controls or the like is calculated (Step 402). Forexample, a distant electric field in a position at a distance of 3 mfrom the subject to be measured is calculated.

[0029] Next, Fourier transformation is performed on the basis of thedistant electric field E(t) in time domain to a distant electric fieldE(f) in frequency domain (Step 403).

[0030] Through the above processing, the electric field to frequencycharacteristics E(f) can be obtained on the basis of the magnetic fieldto time characteristics H(t). Then, of the electric field to frequencycharacteristics E(f) obtained thus, frequency characteristics in whichan electric field value exceeds a setting value are extracted (Step404).

[0031] Finally, current to time characteristics I(t) having theextracted frequency characteristics are concluded on the basis of theabove-mentioned stored information about the current to timecharacteristics I(t) and a position on the subject to be measured, and afitted position on the subject to be measured is outputted (Step 405).

[0032] From this result, it is possible to obtain the magnitude, phaseand position of a current acting a source of electromagnetic waves inthe subject to be measured, which is a predominant factor of theelectromagnetic waves 1 in the distance. Based on this, a measure tocontrol the electromagnetic waves is taken.

[0033] In such a manner, magnetic field to time characteristicsgenerated from a subject to be measured are measured in a plurality ofpositions, and the plurality of measured magnetic field to timecharacteristics are used to calculate electric field to frequencycharacteristics generated from the subject to be measured. In addition,positions in question in the subject to be measured are also detected bycalculation on the basis of the measured magnetic field to timecharacteristics. Accordingly, it is not necessary to measure both thedistant field and the near field as in the conventional case, and it ispossible to shorten the probing time. Particularly, even if there is alarge number of frequency components which do not satisfy a regulationvalue, it is not necessary to measure electromagnetic field distributionnear the subject to be measured in accordance with the number of thesefrequency components as in the conventional case, but it is possible toobtain the places to be coped with by calculation simply. It istherefore possible to shorten the probing time on a large scale.

[0034] Next, another example for calculating current distribution on thebasis of the magnetic field to time characteristics H(t) described inthe above-mentioned flow chart will be described.

[0035] First, the concept of this example will be described. FIG. 2 is adiagram showing the concept. In FIG. 2, very small lattice points (201,203, 204, and so on) in which an electric current is assumed to existare established in a subject to be measured A, and very small latticepoints (205 and so on) in which a magnetic field generated from thesubject to be measured A is measured are established in a measurementarea B.

[0036] In FIG. 2, the reference numeral 201 represents a lattice pointwhere an electric current is assumed to exist; 202, a lattice pointwhere a magnetic field is measured; 203, a lattice point where anelectric current exists actually; 204, a lattice point where an electriccurrent is assumed to exist; 205, a three-dimensional probe formeasuring a magnetic field; 206, a measured magnetic field compositecomplex vector obtained by measurement; 207, a calculated magnetic fieldcomposite complex vector obtained by calculation; and 208, an anglebetween the measured magnetic field composite complex vector 206 and thecalculated magnetic field composite complex vector 207.

[0037] In this calculation system, magnetic field distribution when apredetermined current exists in each lattice point of the subject to bemeasured A is obtained by calculation, and it is judged whether thisobtained result (the calculated magnetic field composite complex vector207) coincides with an actually measured value (the measured magneticfield composite complex vector 206) within an allowable range. If theyare coincide, an electric current is regarded as existing in the latticepoint, and current distribution (position and magnitude) is calculatedper sampling time. The coincidence is judged by using the angle 208between the measured magnetic field composite complex vector 206 and thecalculated magnetic field composite complex vector 207.

[0038] Description will be made about a function used for thiscalculation.

[0039] On the assumption that x, y and z directional components Ix, Iyand Iz of a current exist in a very small lattice point n of the subjectto be measured A, vector potential A in a very small lattice point m inthe measurement area B can be expressed as a function of time t as shownin Expression 2. $\begin{matrix}{{A(t)} = {{{{\frac{1}{2\pi}{\int_{- \infty}^{\infty}{{A(w)}^{{- {j\omega}}\quad t}{\omega}}}} \equiv {\frac{1}{2\pi}{\sum\limits_{f = 0}^{fe}{{A( {2\pi \quad f} )}c^{{- {j2}}\quad \pi \quad {fdt}}\Delta \quad f}}}}\because{A(\omega)}} = {\frac{1}{4\pi}{\int{\frac{J}{r}^{{- j}\quad {kr}}{v}}}}}} & \text{Expression~~2}\end{matrix}$

[0040] Here, J designates current density; ω, an angular frequency; fe,an upper limit of a frequency band which is a target of measurement; andrmn, a distance between the lattice point m and the lattice point n.

[0041] From Maxwell's equations shown in Expression 3, this Expression 2can be expressed as a function of time t with respect to a magneticfield shown in Expression 4. Magnetic field distribution at each latticepoint in the measurement area B is calculated with this Expression 4.Then, Expression 4 is derived on the assumption that a pulse currenthaving a magnitude of 1 and a phase of 0 exists in respective directionsof XYZ coordinate systems at each lattice point in the subject to bemeasured A. With this assumed current, Expression 4 obtains magneticfield distribution generated at each lattice point (measurement point)in the measurement area. Here, time terms of the current are omitted forsimplification.

[0042] Expression 3

H=∇×A

[0043] $\begin{matrix}\begin{matrix}{{{Hm}_{x}( {m,t} )} = \quad {\sum\limits_{n = 1}^{N}\{ {{{{Hx}_{y}( {m,n,t} )}{{Iy}(n)}} + {{{Hx}_{z}( {{mn},t} )}{{Iz}(n)}}} \}}} \\{{{Hm}_{y}( {m,t} )} = \quad {\sum\limits_{n = 1}^{N}\{ {{{{Hy}_{z}( {m,n,t} )}{{Iz}(n)}} + {{{Hy}_{x}( {m,n,t} )}{{Ix}(n)}}} \}}} \\{{{Hm}_{z}( {m,t} )} = \quad {\sum\limits_{n = 1}^{N}\{ {{H\quad {z_{x}( {m,n,t} )}{{Ix}(n)}} + {H\quad {z_{y}( {m,n,t} )}{{Iy}(n)}}} \}}}\end{matrix} & \text{Expression~~4}\end{matrix}$

[0044] Upon the magnetic field distribution calculated with Expression 4and the measured magnetic field distribution in the XYZ coordinatedirections at each lattice point in the measurement area B, complexvectors having a number of dimensions equal to the number of latticesassociated with the respective magnetic field distribution areestablished, and an arithmetic operation as shown in Expression 5 iscarried out upon each term of these complex vectors. That is, the innerproduct of the both complex vectors is obtained. $\begin{matrix}\begin{matrix}{{\sum\limits_{m = 1}^{M}{{{{Hm}_{x}( {m,t} )} \cdot {Hx}_{y}}( {m,n^{\prime},t} )}} = \quad {\sum\limits_{m = 1}^{M}{\sum\limits_{n = 1}^{N}\{ {\underset{\_}{{{Hx}_{y}( {m,n,t} )} \cdot {{Iy}(n)} \cdot {{Hx}_{y}( {m,n^{\prime},t} )}} + {{{Hx}_{x}( {m,n,t} )} \cdot {{Iz}(n)} \cdot {{Hx}_{y}( {m,n^{\prime},t} )}}} \}}}} \\{{\sum\limits_{m = 1}^{M}{{{{Hm}_{x}( {m,t} )} \cdot {Hx}_{z}}( {m,n^{\prime},t} )}} = \quad {\sum\limits_{m = 1}^{M}{\sum\limits_{n = 1}^{N}\{ {{{{Hx}_{y}( {m,n,t} )} \cdot {{Iy}(n)} \cdot {{Hx}_{z}( {m,n^{\prime},t} )}} + \underset{\_}{{{Hx}_{z}( {m,n,t} )} \cdot {{Iz}(n)} \cdot {{Hx}_{z}( {m,n^{\prime},t} )}}} \}}}} \\{{\sum\limits_{m = 1}^{M}{{{Hm}_{y}( {m,t} )} \cdot {{Hy}_{z}( {m,n^{\prime},t} )}}} = \quad {\sum\limits_{m = 1}^{M}{\sum\limits_{n = 1}^{N}\{ {\underset{\_}{{{Hy}_{x}( {m,n,t} )} \cdot {{Iz}(n)} \cdot {{Hy}_{z}( {m,n^{\prime},t} )}} + {{{Hy}_{x}( {m,n,t} )} \cdot {{Ix}(n)} \cdot {{Hy}_{z}( {m,n^{\prime},t} )}}} \}}}} \\{{\sum\limits_{m = 1}^{M}{{{Hm}_{y}( {m,t} )} \cdot {{Hy}_{x}( {m,n^{\prime},t} )}}} = \quad {\sum\limits_{m = 1}^{M}{\sum\limits_{n = 1}^{N}\{ {{{{Hy}_{z}( {m,n,t} )} \cdot {{Iz}(n)} \cdot {{Hy}_{x}( {m,n^{\prime},t} )}} + \underset{\_}{{{Hy}_{x}( {m,n,t} )} \cdot {{Ix}(n)} \cdot {{Hy}_{x}( {m,n^{\prime},t} )}}} \}}}} \\{{\sum\limits_{m = 1}^{M}{{{{Hm}_{z}( {m,t} )} \cdot H}\quad {z_{x}( {m,n^{\prime},t} )}}} = \quad {\sum\limits_{m = 1}^{M}{\sum\limits_{n = 1}^{N}\{ {\underset{\_}{H\quad {{z_{x}( {m,n,t} )} \cdot {{Ix}(n)} \cdot H}\quad {z_{x}( {m,n^{\prime},t} )}} + {H\quad {{z_{y}( {m,n,t} )} \cdot {{Iy}(n)} \cdot H}\quad {z_{x}( {m,n^{\prime},t} )}}} \}}}} \\{{\sum\limits_{m = 1}^{M}{{{{Hm}_{z}( {m,t} )} \cdot H}\quad {z_{y}( {m,n^{\prime},t} )}}} = \quad {\sum\limits_{m = 1}^{M}{\sum\limits_{n = 1}^{N}\{ {{H\quad {{z_{x}( {m,n,t} )} \cdot {{Ix}(n)} \cdot H}\quad {z_{y}( {m,n^{\prime},t} )}} + \underset{\_}{H\quad {{z_{y}( {m,n,t} )} \cdot {{Iy}(n)} \cdot H}\quad {z_{y}( {m,n^{\prime},t} )}}} \}}}}\end{matrix} & \text{Expression~~5}\end{matrix}$

[0045] Here, n′ designates a lattice point where the assumed unitcurrent exists in the subject to be measured A.

[0046] If two equations where current components contained in theunderlined portions in Expression 5 are equal to each other are pickedup and the inner product of these equations is obtained as follows.$\begin{matrix}\begin{matrix}{{\sum\limits_{m = 1}^{M}{{{Hm}_{y}( {m,t} )} \cdot {{Hy}_{x}( {m,n^{\prime},t} )} \cdot {\sum\limits_{m = 1}^{M}{{{{Hm}_{x}( {m,t} )} \cdot H}\quad {z_{x}( {m,n^{\prime},t} )}}}}} = \quad {\sum\limits_{m = 1}^{M}{\sum\limits_{n = 1}^{N}\lbrack {\{ {{{{Hy}_{x}( {m,n,t} )} \cdot {{Iz}(n)} \cdot {{Hy}_{x}( {m,n^{\prime},t} )}} + {{{Hy}_{x}( {m,n,t} )} \cdot {{Ix}(n)} \cdot {{Hy}_{x}( {m,n^{\prime},t} )}}} \} \cdot} }}} \\{\quad \{ {{H\quad {{z_{x}( {m,n,t} )} \cdot {{Ix}(n)} \cdot H}\quad {z_{x}( {m,n^{\prime},t} )}} + {H\quad {{z_{y}( {m,n,t} )} \cdot {{Iy}(n)} \cdot H}\quad {z_{x}( {m,n^{\prime},t} )}}} \}} \\{= \quad {\sum\limits_{m = 1}^{M}{\sum\limits_{n = 1}^{N}\{ {{{{{Hy}_{z}( {m,n,t} )} \cdot {{Iz}(n)} \cdot {{Hy}_{x}( {m,n^{\prime},t} )} \cdot H}\quad {{z_{x}( {m,n,t} )} \cdot {{Ix}(n)} \cdot H}\quad {z_{x}( {m,n^{\prime},t} )}} +} }}} \\{\quad {{{{{Hy}_{z}( {m,n,t} )} \cdot {{Iz}(n)} \cdot {{Hy}_{x}( {m,n^{\prime},t} )} \cdot H}\quad {{z_{y}( {m,n,t} )} \cdot {{Iy}(n)} \cdot H}\quad {z_{x}( {m,n^{\prime},t} )}} +}} \\{\quad {{{{{Hy}_{x}( {m,n,t} )} \cdot {{Ix}(n)} \cdot {{Hy}_{x}( {m,n^{\prime},t} )} \cdot H}\quad {{z_{x}( {m,n,t} )} \cdot {{Ix}(n)} \cdot H}\quad {z_{x}( {m,n^{\prime},t} )}} +}} \\{\quad  {{{{Hy}_{x}( {m,n,t} )} \cdot {{Ix}(n)} \cdot {{Hy}_{x}( {m,n^{\prime},t} )} \cdot H}\quad {{z_{y}( {m,n,t} )} \cdot {{Iy}(n)} \cdot H}\quad {z_{x}( {m,n^{\prime},t} )}} \}} \\{= \quad {{\sum\limits_{m = 1}^{M}{\sum\limits_{n = 1}^{N}\{ {{{{Hy}_{z}( {m,n,t} )} \cdot {{Iz}(n)} \cdot {{Hy}_{x}( {m,n^{\prime},t} )} \cdot H}\quad {{z_{x}( {m,n,t} )} \cdot {{Ix}(n)} \cdot H}\quad {z_{x}( {m,n^{\prime},t} )}} \}}} +}} \\{\quad {{\sum\limits_{m = 1}^{M}{\sum\limits_{n = 1}^{N}\{ {{{{Hy}_{z}( {m,n,t} )} \cdot {{Iz}(n)} \cdot {{Hy}_{x}( {m,n^{\prime},t} )} \cdot H}\quad {{z_{y}( {m,n,t} )} \cdot {{Iy}(n)} \cdot H}\quad {z_{x}( {m,n^{\prime},t} )}} \}}} +}} \\{\quad {{\sum\limits_{m = 1}^{M}{\sum\limits_{n = 1}^{N}\{ {{{{Hy}_{x}( {m,n,t} )} \cdot {{Ix}(n)} \cdot {{Hy}_{x}( {m,n^{\prime},t} )} \cdot H}\quad {{z_{x}( {m,n,t} )} \cdot {{Ix}(n)} \cdot H}\quad {z_{x}( {m,n^{\prime},t} )}} \}}} +}} \\{\quad {\sum\limits_{m = 1}^{M}{\sum\limits_{n = 1}^{N}\{ {{{{Hy}_{x}( {m,n,t} )} \cdot {{Ix}(n)} \cdot {{Hy}_{x}( {m,n^{\prime},t} )} \cdot H}\quad {{z_{y}( {m,n,t} )} \cdot {{Iy}(n)} \cdot H}\quad {z_{x}( {m,n^{\prime},t} )}} \}}}}\end{matrix} & \text{Expression~~6}\end{matrix}$

[0047] On the other hand, if the position of a measured point in themeasurement area B is provided to enclose a portion above the subject tobe measured A which is a source of electromagnetic waves, the conditionsof Expression 7 are established. As a result, the first term, the secondterm and the fourth term of Expression 6 become zero, so that Expression6 can be simplified as shown in Expression 8. $\begin{matrix}\begin{matrix}{{\theta \leq \quad {\pm {\arctan ( \frac{\sqrt{X_{p}^{2} + Y_{p}^{2}}}{( {Z_{p} - Z_{s}} )} )}}} = {\pm \theta^{\prime}}} \\{\varphi \leq \quad {\pm 180^{\circ}}} \\{{\sum\limits_{m = 1}^{M}\sum\limits_{n = 1}^{N}} = \quad {\int_{- \theta^{\prime}}^{+ \theta^{\prime}}{\int_{{- 180}{^\circ}}^{{+ 180}{^\circ}}{{\varphi}{\theta}}}}}\end{matrix} & \text{Expression~~7} \\{{\sum\limits_{m = 1}^{M}{{{Hm}_{y}( {m,t} )} \cdot {{Hy}_{x}( {m,n^{\prime},t} )} \cdot {\sum\limits_{m = 1}^{M}{{{{Hm}_{x}( {m,t} )} \cdot H}\quad {z_{x}( {m,n^{\prime},t} )}}}}} = {\sum\limits_{m = 1}^{M}{\sum\limits_{n = 1}^{N}\{ {{{{Hy}_{x}( {m,n,t} )} \cdot {{Ix}(n)} \cdot {{Hy}_{x}( {m,n^{\prime},t} )} \cdot {{Hz}_{x}( {m,n,t} )} \cdot {{Ix}(n)} \cdot H}\quad {z_{x}( {m,n^{\prime},t} )}} \}}}} & \text{Expression~~8}\end{matrix}$

[0048] Similarly, other components of the XYZ coordinate systems can bealso expressed as shown in Expression 9. $\begin{matrix}{{{\sum\limits_{m = 1}^{M}{{{Hm}_{x}( {m,t} )} \cdot {{Hx}_{y}( {m,n^{\prime},t} )} \cdot {\sum\limits_{m = 1}^{M}{{{{Hm}_{x}( {m,t} )} \cdot H}\quad {z_{y}( {m,n^{\prime},t} )}}}}} = {\sum\limits_{m = 1}^{M}{\sum\limits_{n = 1}^{N}\{ {{{{Hx}_{y}( {m,n,t} )} \cdot {{Iy}(n)} \cdot {{Hx}_{y}( {m,n^{\prime},t} )} \cdot {{Hz}_{y}( {m,n,t} )} \cdot {{Iy}(n)} \cdot H}\quad {z_{y}( {m,n^{\prime},t} )}} \}}}}{{\sum\limits_{m = 1}^{M}{{{Hm}_{x}( {m,t} )} \cdot {{Hx}_{x}( {m,n^{\prime},t} )} \cdot {\sum\limits_{m = 1}^{M}{{{{Hm}_{y}( {m,t} )} \cdot H}\quad {y_{x}( {m,n^{\prime},t} )}}}}} = {\sum\limits_{m = 1}^{M}{\sum\limits_{n = 1}^{N}\{ {{{{Hx}_{z}( {m,n,t} )} \cdot {{Iz}(n)} \cdot {{Hx}_{z}( {m,n^{\prime},t} )} \cdot {{Hy}_{z}( {m,n,t} )} \cdot {{Iz}(n)} \cdot H}\quad {y_{z}( {m,n^{\prime},t} )}} \}}}}} & \text{Expression~~9}\end{matrix}$

[0049] Since the Expressions 8 and 9 express inner productsrespectively, if these inner products are divided by the magnitudes ofthe complex vectors corresponding to the above-mentioned measured valueand calculated value, it is possible to calculate the matching degree(cos θ) between the magnetic field distribution (calculated value) andthe magnetic field distribution (measured value) can be calculated. Thisis a probability (or ratio) in which a source of electromagnetic waves(an electric current) exists in each lattice point in the subject to bemeasured A. Accordingly, it is possible to conclude that an electriccurrent exists in the lattice point if the matching degree is large.

[0050] This probability of existence of an electric current is expressedby Expression 10. $\begin{matrix}\begin{matrix}{{\cos \quad \theta_{({{Ix}{(n)}})}} = \quad \sqrt{\frac{\sum\limits_{m = 1}^{M}{\{ {{{Hm}_{y}( {m,t} )} \cdot {{Hy}_{x}( {m,n,t} )}} \} \cdot {\sum\limits_{m = 1}^{M}\{ {{{{Hm}_{z}( {m,t} )} \cdot H}\quad {z_{x}( {m,n,t} )}} \}}}}{\sum\limits_{m = 1}^{M}{\sum\limits_{n = 1}^{N}\{ {{{{Hy}_{x}( {m,n,t} )}^{2} \cdot H}\quad {z_{x}( {m,n,t} )}^{2}} \}}}}} \\{= \quad \sqrt{\frac{{{{{Hm}_{y}( {m,t} )} \cdot {{Hy}_{x}( {m,n,t} )}}} \cdot {{{{{Hm}_{z}( {m,t} )} \cdot H}\quad {z_{x}( {m,n,t} )}}}}{{{{Hy}_{x}( {m,n,t} )}}^{2} \cdot {{H\quad {z_{x}( {m,n,t} )}}}^{2}}}} \\{{\cos \quad \theta_{({{Iy}{(n)}})}} = \quad \sqrt{\frac{\sum\limits_{m = 1}^{M}{\{ {{{{Hm}_{z}( {m,t} )} \cdot H}\quad {z_{y}( {m,n,t} )}} \} \cdot {\sum\limits_{m = 1}^{M}\{ {{{{Hm}_{x}( {m,t} )} \cdot H}\quad {x_{y}( {m,n,t} )}} \}}}}{\sum\limits_{m = 1}^{M}{\sum\limits_{n = 1}^{N}\{ {H\quad {{z_{y}( {m,n,t} )}^{2} \cdot H}\quad {x_{y}( {m,n,t} )}^{2}} \}}}}} \\{= \quad \sqrt{\frac{{{{{{Hm}_{x}( {m,t} )} \cdot H}\quad {z_{y}( {m,n,t} )}}} \cdot {{{{{Hm}_{x}( {m,t} )} \cdot H}\quad {x_{y}( {m,n,t} )}}}}{{{H\quad {z_{y}( {m,n,t} )}}}^{2} \cdot {{H\quad {x_{y}( {m,n,t} )}}}^{2}}}} \\{{\cos \quad \theta_{({{Iz}{(n)}})}} = \quad \sqrt{\frac{\sum\limits_{m = 1}^{M}{\{ {{{{Hm}_{x}( {m,t} )} \cdot H}\quad {x_{z}( {m,n,t} )}} \} \cdot {\sum\limits_{m = 1}^{M}\{ {{{{Hm}_{y}( {m,t} )} \cdot H}\quad {y_{z}( {m,n,t} )}} \}}}}{\sum\limits_{m = 1}^{M}{\sum\limits_{n = 1}^{N}\{ {H\quad {{y_{z}( {m,n,t} )}^{2} \cdot H}\quad {x_{z}( {m,n,t} )}^{2}} \}}}}} \\{= \quad \sqrt{\frac{{{{{{Hm}_{x}( {m,t} )} \cdot H}\quad {x_{z}( {m,n,t} )}}} \cdot {{{{{Hm}_{x}( {m,t} )} \cdot H}\quad {x_{y}( {m,n,t} )}}}}{{{H\quad {z_{y}( {m,n,t} )}}}^{2} \cdot {{H\quad {x_{z}( {m,n,t} )}}}^{2}}}}\end{matrix} & \text{Expression~~10}\end{matrix}$

[0051] If the matching degree (cos θ) satisfies the conditions shown inExpression 11, an electric current is regarded as existing at thelattice point, and the value following “then” is calculated. If thematching degree (cos θ) does not satisfy the conditions, an electriccurrent is regarded as not existing at the lattice point, and anarithmetic operation to make the value following “else” be 0 isperformed. $\begin{matrix}{{{\text{If}\quad \cos \quad \theta_{({{Ix}{(n^{\prime})}})}} \geq \frac{{dx}/2}{\sqrt{( {{dx}/2} )^{2} + ( {z_{p} - z_{a}} )^{2}}}}{{\text{then}\quad {{Ix}( n^{\prime} )}} = {{\sqrt{\frac{{Hm}_{y}( {m,t} )}{{Hy}_{x}( {m,n,t^{\prime}} )} \cdot \frac{{Hm}_{z}( {m,t} )}{H\quad {z_{x}( {m,n,t^{\prime}} )}}}\quad \text{else}\quad {{Ix}( n^{\prime} )}} = 0}}{{\text{If}\quad \cos \quad \theta_{({{Iy}{(n^{\prime})}})}} \geq \frac{{dy}/2}{\sqrt{( {{dy}/2} )^{2} + ( {z_{p} - z_{a}} )^{2}}}}{{\text{then}\quad {{Iy}( n^{\prime} )}} = {{\sqrt{\frac{{Hm}_{z}( {m,t} )}{H\quad {z_{y}( {m,n,t^{\prime}} )}} \cdot \frac{{Hm}_{x}( {m,t} )}{H\quad {x_{y}( {m,n,t^{\prime}} )}}}\quad \text{else}\quad {{Iy}( n^{\prime} )}} = 0}}{{\text{If}\quad \cos \quad \theta_{({{Iz}{(n^{\prime})}})}} \geq \frac{{dz}/2}{\sqrt{( {{dz}/2} )^{2} + ( {z_{p} - z_{a}} )^{2}}}}{{\text{then}\quad {{Iz}( n^{\prime} )}} = {{\sqrt{\frac{{Hm}_{x}( {m,t} )}{H\quad {x_{z}( {m,n,t^{\prime}} )}} \cdot \frac{{Hm}_{y}( {m,t} )}{H\quad {y_{z}( {m,n,t^{\prime}} )}}}\quad \text{else}\quad {{Iz}( n^{\prime} )}} = 0}}} & \text{Expression~~11}\end{matrix}$

[0052] Thus, by using calculated values and measured values aboutmagnetic field distribution per sampling time, and Expressions 10 and11, it is possible to calculate current to time characteristics I(t) onthe basis of the above-mentioned magnetic field to time characteristicsH(t).

[0053] This manner requires only calculation time proportional to thesquare of a lattice number (m, n) while the above-mentioned manner basedon simultaneous equations requires calculation time proportional to thecube of the lattice number. Accordingly, it is possible to shorten thecalculation time on a large scale.

[0054]FIG. 3 shows a flow chart which is actually processed with thisconcept.

[0055] Here, in the first sampling, a source of electromagnetic waves isprobed. In the second and following samplings, an assumed pulse currentis delayed in accordance with the sampling time. When the pulse currentis delayed in accordance with the sampling frequency at the time ofmeasurement in such a manner, it is possible to obtain the time waveformof an actual current. In FIG. 3, (a, b, c) is applied to all the casesof (x, y, z), (y, z, x) and (z, x, y) . That is, an arithmetic operationis performed by replacing (a, b, c) by (x, y, z), (y, z, x) or (z, x,y). Also in the process of FIG. 3, lattice points on the subject to bemeasured A and lattice points in the measurement area B as shown in FIG.2 are established.

[0056] Description will be made about the case where (a, b, c) is (x, y,z) . A pulse current in the x-direction is assumed to exist at a latticepoint which is on the subject to be measured A, and calculated values(Hyx(m, n, t) and Hzx(m, n, t)) of y-directional and z-directionalmagnetic fields perpendicular to this pulse current are calculated (Step301 a, b). This calculation is carried out upon each lattice point.

[0057] In addition, y-directional and z-directional magnetic fields(Hmy(m, t) and Hmz(m, t)) at a lattice point in the measurement area aremeasured (Step 302 a,b). This measurement is carried out upon eachlattice point.

[0058] By using these calculated values, measured values, andExpressions 10 and 11, lattice points (positions) where a current existsin the subject to be measured A and the current values of the latticepoints are calculated (Step 303). That is, the probabilities (cos è) inwhich a current exists at each lattice point are calculated on the basisof Expression 11, and current values at the lattice points satisfyingthe conditions of cos θ shown in Expression 11 are calculated. Thearithmetic operation of Expression 10 includes an arithmetic operationof the inner product between the calculated value 301 a and the measuredvalue 302 a every time step of ½fe (Step 303-1 a), an arithmeticoperation of the inner product between the calculated value 301 b andthe measured value 302 b every time step of ½fe (Step 303-1 b), and anarithmetic operation of the inner product between the inner productarithmetic operation results (303-1 a and 303-1 b) (Step 303-2).

[0059] Such an arithmetic operation is performed upon measured valuesevery sampling time step, so that the position of a source ofelectromagnetic waves and the time waveform of a current in the positionare calculated (Step 304).

[0060] Further, a similar arithmetic operation is performed upon pulsecurrents which are assumed to exist in the respective x-, y- andz-directions, and the positions and time waveforms of perpendicularcurrent components are used (Step 305). The time waveform of electricfield intensity in a distance where the electric field intensity iscontrolled is calculated every sampling step (Step 306).

[0061] The calculated time waveform E(t) of the electric field intensityis Fourier-transformed from time domain to frequency domain, so that aspectrum E(f) in the distant electric field is calculated (Step 307).

[0062] By using the distant electric field spectrum E(f), comparison ismade between electric field intensity in each frequency and a regulationvalue (Step 308). It is concluded which frequency components ofelectromagnetic waves generated by the subject to be measured exceed theregulation value.

[0063] The processing for the frequency components exceeding theregulation value is as mentioned above. Electric currents having thefrequency components are calculated, and positions of lattice pointswhere the currents exist are outputted.

[0064] In the above processing, it is not necessary to measure both thedistant field and the near field as in the conventional case beforeplaces to be coped with are specified. In addition, even if there aremany frequency components which do not satisfy the regulation value, itis not necessary to measure electromagnetic field distribution near thesubject to be measured in accordance with the number of the frequencycomponents as conventionally. It is therefore possible to shorten theprobing time.

[0065] As described above, if the three-dimensional probes are disposedin an array to simultaneously measure the near magnetic field in theform of time waveforms at various measuring points so as not to producea time difference between the measurement points, it is possible to makethe sampling start clock 112 unnecessary. In this case, it will go wellif the position and time waveform of a current as a source ofelectromagnetic waves on the subject to be measured are calculated onthe basis of amplitudes (A1, A2, . . . An) and time delays (t1, t2, . .. tn) of measured values.

[0066] In addition, although description has been made about atwo-dimensional subject to be measured such as a circuit board, it isalso possible to probe the frequency, magnitude, phase and position of asource of electromagnetic waves in a three-dimensional electronicapparatus if an assumed position of the source of electromagnetic wavesis extended to a space occupied by the three-dimensional subject to bemeasured and calculation is made on such a space.

[0067] According to the present invention, it is not necessary tomeasure both the distant field and the near field as in the conventionalcase before places to be coped with are specified. In addition, even ifthere are many frequency components which do not satisfy the regulationvalue, it is not necessary to measure electromagnetic field distributionnear the subject to be measured in accordance with the number of thefrequency components as in the conventional case. It is thereforepossible to shorten the probing time.

1. An electromagnetic wave source probing method comprising the stepsof: measuring magnetic field to time characteristics generated from asubject to be measured in a plurality of positions; calculating electricfield to frequency characteristics generated from said subject to bemeasured by use of said plurality of measured magnetic field to timecharacteristics; extracting frequency components exceeding apredetermined electric field value in said calculated electric field tofrequency characteristics; and outputting positions where currentshaving said extracted frequency components exist in said subject to bemeasured.
 2. An electromagnetic wave source probing method according toclaim 1, wherein said magnetic field to time characteristics aremeasured by a plurality of probes disposed longitudinally andtransversely respectively.
 3. An electromagnetic wave source probingmethod according to claim 1, wherein said electric field to frequencycharacteristics are characteristics at a legal-controlled distance fromsaid subject to be measured.
 4. An electromagnetic wave source probingmethod according to claim 2, wherein said electric field to frequencycharacteristics are characteristics at a legal-controlled distance fromsaid subject to be measured.
 5. An electromagnetic wave source probingmethod according to claim 1, wherein current to time characteristics ina plurality of positions are calculated from said plurality of magneticfield to time characteristics, and electric field to frequencycharacteristics generated from said substance to be measured arecalculated from said calculated current to time characteristics.
 6. Anelectromagnetic wave source probing method according to claim 2, whereincurrent to time characteristics in a plurality of positions arecalculated from said plurality of magnetic field to timecharacteristics, and electric field to frequency characteristicsgenerated from said subject to be measured are calculated from saidcalculated current to time characteristics.
 7. An electromagnetic wavesource probing method according to claim 3, wherein current to timecharacteristics in a plurality of positions are calculated from saidplurality of magnetic field to time characteristics, and electric fieldto frequency characteristics generated from said subject to be measuredare calculated from said calculated current to time characteristics. 8.An electromagnetic wave source probing method according to claim 5,wherein current to time characteristics including electric currentshaving said extracted frequency components are calculated, and positionsin said subject to be measured having said calculated current to timecharacteristics are outputted.
 9. An electromagnetic wave source probingmethod according to claim 6, wherein current to time characteristicsincluding electric currents having said extracted frequency componentsare calculated, and positions in said subject to be measured having saidcalculated current to time characteristics are outputted.
 10. Anelectromagnetic wave source probing method according to claim 7, whereincurrent to time characteristics including electric currents having saidextracted frequency components are calculated, and positions in saidsubject to be measured having said calculated current to timecharacteristics are outputted.
 11. An electromagnetic wave sourceprobing device comprising: a plurality of measuring means for measuringmagnetic field to time characteristics generated from a subject to bemeasured; a first calculating means for calculating electric field tofrequency characteristics generated from said subject to be measuredbased on said measured magnetic field to time characteristics; a secondcalculating means for calculating frequency components exceeding apredetermined electric field value in said calculated electric field tofrequency characteristics; and an output means for outputting positionswhere currents having said calculated frequency components exist in saidsubject to be measured.
 12. An electromagnetic wave source probingdevice according to claim 11, wherein said magnetic field to timecharacteristics are measured by a plurality of probes arrangedlongitudinally and transversely respectively.
 13. An electromagneticwave source probing device according to claim 11, wherein said electricfield to frequency characteristics are characteristics at alegal-controlled distance from said subject to be measured.
 14. Anelectromagnetic wave source probing device according to claim 12,wherein said electric field to frequency characteristics arecharacteristics at a legal-controlled distance from said subject to bemeasured.
 15. An electromagnetic wave source probing device according toclaim 11, wherein said first calculating means calculates current totime characteristics in a plurality of positions in said substance to bemeasured on the basis of said plurality of magnetic field to timecharacteristics, and calculate electric field to frequencycharacteristics generated from said subject to be measured by use ofsaid calculated current to time characteristics.
 16. An electromagneticwave source probing device according to claim 12, wherein said firstcalculating means calculates current to time characteristics in aplurality of positions in said substance to be measured on the basis ofsaid plurality of magnetic field to time characteristics, and calculateelectric field to frequency characteristics generated from said subjectto be measured by use of said calculated current to timecharacteristics.
 17. An electromagnetic wave source probing deviceaccording to claim 13, wherein said first calculating means calculatescurrent to time characteristics in a plurality of positions in saidsubstance to be measured on the basis of said plurality of magneticfield to time characteristics, and calculate electric field to frequencycharacteristics generated from said subject to be measured by use ofsaid calculated current to time characteristics.
 18. An electromagneticwave source probing device according to claim 14, wherein said firstcalculating means calculates current to time characteristics in aplurality of positions in said substance to be measured on the basis ofsaid plurality of magnetic field to time characteristics, and calculateelectric field to frequency characteristics generated from said subjectto be measured by use of said calculated current to timecharacteristics.
 19. An electromagnetic wave source probing deviceaccording to claim 15, wherein said output means calculates current totime characteristics including currents having said extracted frequencycomponents, and outputs positions in said subject to be measured havingsaid calculated current to time characteristics.
 20. An electromagneticwave source probing device according to claim 16, wherein said outputmeans calculates current to time characteristics including currentshaving said extracted frequency components, and outputs positions insaid subject to be measured having said calculated current to timecharacteristics.
 21. An electromagnetic wave source probing deviceaccording to claim 17, wherein said output means calculates current totime characteristics including currents having said extracted frequencycomponents, and outputs positions in said subject to be measured havingsaid calculated current to time characteristics.
 22. An electromagneticwave source probing device according to claim 18, wherein said outputmeans calculates current to time characteristics including currentshaving said extracted frequency components, and outputs positions insaid subject to be measured having said calculated current to timecharacteristics.